1. Field of the Invention
This invention relates to a thermoplastic resin composition that is superior in impact resistance, heat resistance, mechanical strength, moldability, and fluidity, more specifically, to a thermoplastic resin composition comprising at least one resin (A) selected from the group consisting of a polyester resin and a polycarbonate resin, and an aromatic polyester-polyorganosiloxane block copolymer (B).
2. Description of the Prior Art
Polyester resins, depending on the composition, are molding materials having high heat resistance and high strength, including a variety of types ranging from general-purpose types to high-performance types. However, these polyester resins generally are insufficient in impact resistance and, especially, a considerable decrease in strength is seen when an impact is exerted on a test specimen provided with a notch.
There have been made many attempts to improve the impact strength. For example, polybutylene terephthalate resin (PBT) is often blended with a rubber component having a low glass-transition temperature (Tg). Such rubber components are roughly divided into four types: ethylene copolymers, butadiene rubber, acrylic rubber, and flexible polyesters (such as PBT/PTMG copolymer). However, with these rubber components added, the polyester resins yet have problems of inferior weatherability and heat resistance, and the blending is not an improvement of impact strength while maintaining the advantageous properties of the polyester resins.
Polycarbonate resin is known as a superior molding material having high impact strength and toughness, high transparency, good dimensional stability, good creep resistance, and good fire retardant properties. However, impact strength of polycarbonate resin is dependent on thickness, and thick products are extremely low in impact strength. Furthermore, polycarbonate resin is often combined with glass fiber as a filler, which has a bad influence on impact resistance characteristics of the polycarbonate resin.
Thus, it is a primary object of the present invention to provide a thermoplastic resin composition which retains advantageous properties of polyester resin or polycarbonate resin, with improved impact resistance.